Manufacture of thiuram disulfides



atentecl July 1 1947 UNITED STATES PATENT OFFICE MANUFACTURE OF THIURAM DISULFIDES Leslie A. Gillette, Wyandottc, Mich., assignor to Sharples Chemicals Inc., Philadelphia, Pa., a corporation of Delaware No Drawing. Application December 6, 1944, Serial No. 566,951

7 Claims. 1

The present invention pertains to manufacture of symmetrical dialkyl thiuram disulfides and similar compounds containing aryl or aralkyl radicals in place of the alkyl radicals of such compounds. It was developed in connection with research to form compounds of this type containing from 1 to carbon atoms in their alkyl radicals, and it will accordingly be described in reference to that problem, with the understanding that the technique described may be applied in manufacture of other N-substituted thiuram disulfides containing two and only two symmetrically positioned organic radicals. The same technique described herein for manufacture of thiuram disulfides N-eubstituted symmetrically by two alkyl radicals ranging from methyl to amyl may, for example, be employed in manufacture of diphenyl or dibenzyl thiuram disulfide, and manufacture of these compounds is accordingly included within the scope of the invention,

The manufacture of tetra-alkyl thiuram disulfides has heretofore been accomplished in a manner providing satisfactory yields and conversions by oxidation of salts of dialkyl dithiocarbamic acids, as indicated by the following equation based upon the method of manufacture taught in the patent to Olin and Deger, No. 2,325,194:

1. 2RzNCSSNa 2NaNOz 11.61

alkyl thiuram disulfides. It should, theoretically,

be possible to accomplish oxidation of salts of mono-alkyl dithiocarbamic acids by the procedure of oxidation taught by Adams to form symmetrical dialkyl thiuram disulfides as indicated by the following equation:

2. ZRDtTCSSNa H H2S04 RlTTCSSCIqR NazSOl ZHZO In eiiorts to conduct an oxidation reaction of this or other types upon the salts of mono-alkyl dithiocarbamic acids, however, the salts have largely been converted into the free acid which in turn is converted into mustard oil compounds, as indicated by the following equation:

a. RNCSSH nNos HZS Adams (U. S. Patent 1,782,112) even goes so far as to take advantage of the fact that salts of mono-alkyl dithiocarbamic acids tend to be converted to mustard oils when subjected to oxidizing conditions in the presence of corresponding salts of dialkyl dithiocarbamic acids, in separating the constituents of a mixture of amines from each other.

Beilstein (volume 4, page 119, 4th edition) describes manufacture of symmetrical diethyl thiuram disulfide by oxidizing a solution of the mono-ethyl ammonium salt of mono-ethyl dithiocarbamic acid with bromine water or with iodine in alcohol, but this method provides relatively poor yields and an oily product which must be purified by recrystallization. The method of the present invention, on the other hand, provides excellent yields and a white crystalline product without need for further purification.

The present invention rests upon the discovery that, by maintaining a body of aqueous solution containing hydrogen peroxide and a mineral acid, and introducing a salt of a mono-alkyl dithiocarbamic acid gradually into contact with this solution, the desired reaction of Equation 2 can be favored, and the undesired reaction of Equation 3 minimized, thereby producing an excellent grade of symmetrical dialkyl thiuram disulfide in good yield. In the preferred practice of the invention, the salt of mono-alkyl dithiocarbamic acid is preferably introduced progressively beneath the surface of an aqueous solution containing the hydrogen peroxide and sul furic acidor other mineral acid (e. g., hydrochloric acid). While the technique of maintaining the entire body of oxidizing agent in the reaction vessel and introducing the thiocarbamic acid salt to be oxidized gradually into that vessel has an advantage in favoring formation of the desired symmetrical dialkyl thiuram disulfide as compared to undesired formation of mustard oil compounds, regardless of the other specific conditions of the reaction, best results in practice of the invention have been obtained by maintaining the temperature between 0 and 25 C. during the course of the reaction. 1

Since the hydrogen peroxide and mineral acid serving as the oxidizing agents are maintained in aqueous solution during the course of the reaction, it is desirable that the salt of the monoalkyl dithiocarbamic acid to be oxidized be also in the form of an aqueous solution when it is introduced into the aqueous solution containing the hydrogen peroxide and the mineral acid. For this reason, the preferred practice of the invention involves use of salts of mono-alkyl dithiocarbamic acids which are soluble in water, and the preferred salts for use in practice of the invention are the ammonium, substituted ammonium (e. g., alkyl, aralkyl or aryl ammonium) or alkali metal salts of mono-alkyl, mono-aryl or mono-aralkyl dithiocarbamic acids. If the sodium salt is to be used, this salt may be prepared by reacting a mono-alkyl amine with carbon disulfide and sodium hydroxide in accordance with the following equation:

4. ENE; CS NaOH v Rl'VCSSNa 1120 and the resulting sodium salt of the mono-alkyl dithiocarbamic acid may then be oxidized by the reaction of Eqquation 2. Alternatively, carbon disulfide may be reacted with an excess of the mono-alkyl amine to produce a mono-alkyl ammonium salt of the mono-alkyl dithiocarbamic acid as illustrated by the following equation:

The resulting mono-'alkyl ammonium salt of the mono-alkyl dithiocarbamic acid is then oxidized to form the desired dialkyl thiuram disulfide in accordance with the following equation:

RNCSSCNR RNH'meoi 21120 at a A similar procedure may be adopted in condens ing a primary aryl or aralkyl amine with carbon disulfide to form anaryl ammonium salt of a mono-aryl dithiocarbamic acid or an aralkyl ammonium salt of a mono-aralkyl dithiocarbamic acid, and then oxidizing the resulting salt to form the desired diaryl thiuram disulfide or diaralkyl thiuram disulfide, as the case may be.

The following examples illustrate the practice of the invention:

Example I A solution containing 2.0 moles of sodium monoethyldithiocarbamate was prepared in the usual manner by reacting aqueous solutions of sodium hydroxide and'ethylamine with carbon disulfide at a temperature of 20 C. This solution was then slowly introduced with stirring below the surface of a solution containing 1.0 mole of hydrogen peroxide and 1.0 mole of sulfuric acid in 1500 ml. water. The temperature of the reaction was kept between and C. by'means of an ice bath. The time required to introduce the carbamate solution was two hours. The resulting slurry was filtered and washed well with water. The wet filter cake was given a naphtha wash and then dried at room temperature. The dried product was white and had no odor of ethyl isothiocyanate. A yield of 81.4 percent of symmetrical diethyl thiuram disulfide was obtained.

Example II A solution of 4 moles of ethylammonium ethyldithiocarbamate in 27.7 moles of water was added slowly with stirring and cooling to a solution of 2 moles of hydrogen peroxide and 2 moles of sulfuric acid in 166.5 moles of water. The oxidation was carried out at 0 to 25 0., preferably within the range 10 to 15 C. The product was filtered, washed with water and dried at a low temperature to prevent decomposition into ethyl mustard oil. The yield of symmetrical diethyl thiuram disulfide was almost quantitative, being above 99%.

Example III A solution of 1.0 mole of n-butylammonium n-butyldithiocarbamate in 16.5 moles of water was added slowly with stirring and cooling to a solution of 1.0 mole of 28% hydrogen peroxide and 1.0 mole of 95.5% sulfuric acid in 27.5 moles of water. The oxidation was carried out at 1015 C. The solid symmetrical dibutyl thiuram disulfide resulting was washed with water, then with naphtha to remove traces of mustard oil and dried at room temperature.

Example IV A solution of sodium benzyldithiocarbamate is prepared by reacting benzylamine with aqueous sodium hydroxide solution and carbon disulfide. This solution is then slowly introducedbeneath the surface of a solution containing sulfuric acid and hydrogen peroxide in equal molecular quantities. The resulting product is separated from the solution and dried to obtain symmetrical dibenzyl thiuram disulfide.

Various modifications are possible within the scope of the invention, and I do not therefore wish to be limited except by the scope of the following claims.

I claim:

1. In the manufacture of thiuram disulfides N-substituted symmetrically by only two organic radicals chosen from the class consisting of alkyl radicals containing from 1 to 5 carbon atoms, phenyl radicals and benzyl radicals, the process comprising oxidizing a water-soluble salt chosen from the class consisting of the alkali metal and ammonium salts of the corresponding mono-N- substituted dithiocarbamic acid by introducing said salt gradually in the form of an aqueous solution into an aqueous solution containing hydrogen peroxide and a mineral acid while maintaining the reaction mixture at a temperature between 0 and 25 C.

2. In the manufacture of thiuram disulfides N substituted symmetrically by only two organic radicals chosen from the class consisting of alkyl radicals containing from 1 to 5 carbon atoms, phenyl radicals and benzyl radicals, the process compr s n oxidizing a mono-substituted ammonium salt of a mono-N-substituted dithioc'arbamic acid, of which the ammonium substituent and the dithiocarbamic acid substituent both correspond to the organic radicals of the desired thiuram disulfide derivative, by introducing said salt grad- 4. In the manufacture of dialkyl thiuram disulfides containing from 1 to 5 carbon atoms in the alkyl radicals, the process comprising oxidizing an ammonium salt of the mono-alkyl dithiocarbamic acid having the desired alkyl substituent by introducing said salt in the form of an aqueous solution gradually into an aqueous solution containing hydrogen peroxide and a mineral acid.

5. In the manufacture of dialkyl thiuram disulfides containing from 1 to 5 carbon atoms in the alkyl radicals, the process comprising oxidizing an alkyl ammonium salt of the mono-alkyl dithiocarbamic acid having the desired alkyl substituent by introducing said salt in the iorm of an aqueous solution gradually into an aqueous solution containing hydrogen peroxide and a mineral acid.

6. In the manufacture of dialkyl thiuram disulfides containing from 1 to 5 carbon atoms in the alkyl radicals, the process comprising condensing a primary alkyl amine having the carbon content and configuration of the desired alkyl substituent of the thiuram disulfide derivative with carbon disulfide to form a mono-alkyl ammonium salt of a mono-alkyl dithiocarbamic acid, and introducing said salt gradually into an aqueous solution containing hydrogen peroxide and a mineral acid to form the desired thiuram disulfide derivative.

7. In the manufacture of thiuram disulfides N-substituted symmetrically by only two organic radicals chosen from the class consisting of alkyl radicals containing from 1 to 5 carbon atoms, 'phenyl radicals and benzyl radicals, the process comprising oxidizing a water-soluble salt chosen from the class consisting of the alkali metal and ammonium salts of the corresponding mono-N- substituted dithiocarbamic acid by introducing said salt gradually in the form of an aqueous solution into an aqueous solution containing hydrogen peroxide and a mineral acid.

r LESLIE A. GILLETTE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,782,111 Adams Nov. 18, 1930 1,782,112 Adams Nov. 18, 1930 

